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Client:
City of Tacoma |
Background
The City of Tacoma’s Materials Handling Laboratory was formerly
used for testing asphalt with chlorinated solvents. These solvents have
been detected in the groundwater underlying the site.
Challenges
This facility lies within the South Tacoma Channel Superfund site, a square-mile
area where groundwater contaminated with chlorinated solvents is under
remediation. To complicate matters, this heavily industrialized area features
a number of pumping wells that could capture the contaminated groundwater.
Therefore, identifying the source(s) of contamination at the Materials
Handling Laboratory required a combination of effective hydraulic and
chemical analyses.
Approach
Our streamlined RI/FS won approval from the Washington Department of Ecology,
allowing us to investigate the source(s) of contamination using soil gas
results, chemical “fingerprinting,” and groundwater flow patterns.
To assess the potential for nearby pumping wells to capture the contamination,
we first delineated their capture zones and then used a variety of modeling
tools to analyze contaminant flow. We also proposed excavating soils from
source areas identified around the site.
Outcome
Ecology accepted our capture zone report and our proposed source-control
measure of excavating soils from drum-septic and spill areas. Our strategy
for designating “F002” hazardous waste—that is waste
containing less than 10 percent “spent” halogenated solvents—saved
the client about $15,000. This strategy entailed acquiring a “contained-in”
designation for contaminated soils from Ecology prior to excavation.